Here are some difference between Roomba 630 and 655.
Roomba 630 vs 655
images from manufacturer

As far as I know, the Roomba 655 is a Costco model whereas the 630 is a general model that you can buy from official site http://store.irobot.com and other online shopping malls such as Amazon.com and Walmart.com

Scheduling Feature
Both of them belong to the Roomba 600 series, however, the Roomba 630 has no scheduling function while 655 features On-board Scheduling that allows users to preset cleaning times.

Battery
The 655 uses the purple iRobot XLife Extended Life Battery doubles the cleaning cycles of the yellow iRobot Advanced Power System battery which is used on the 630.

More:
* According to iRobot, the 655 also comes with a redesigned side brush that cleans better and easier to remove.

* The 655 has the Dual Voltage Integrated Home Base whereas the 630 uses the Home Base (110V) and regular battery Charger.

* The 655 comes with 2 brush cleaning tools (1 round and 1 flat), 1 extra side brush, 1 extra rubber brush, 1 extra bristle brush, 2 C batteries for Virtual Wall whereas the 630 has only the flat brush cleaning tool, No extra brushes, no batteries for Virtual Wall.

P.S.
Both of them do NOT support Lighthouse that helps Roomba navigate room-to-room.

If you know other difference between Roomba 655 and 630, please share below to help others buy the right one.

The iRobot Roomba 585 was sold at Sam’s Club and Costco, and it has been discontinued. The 655 is available at Costco, it is a simlar model to the 650.
Here are some difference between Roomba 655 and 585.
Roomba 585 vs 655
images from manufacturer

There are 2 apparent difference that you can find easily from the faceplate.

1,
On-board Scheduling
The 655 has the on-board scheduling whereas the 585 is pretty basic and has no scheduling function.
With the scheduling feature, you can preset the cleaning times, then the Roomba will do its job at your desired time, even when you are not at home.

2,
Carrying Handle
The 655 has a handy built in carrying handle for easy transport while the 585 does not include.

Battery
The 655 uses the Xlife Extended Life Battery while the 585 uses the Advanced Power System Battery.
The Xlife battery doubles the time before you may need to replace the battery.

Side Brush
The 655 uses new brush design that’s claimed to be easier to removed.

If you know other difference between the Roomba 585 and 655, please comment below to share your reviews.

Here are some apparent difference between Roomba 595 and 655.
Roomba 595 vs 655
images from manufacturer

Carrying Handle
As you can see from the product images, the 655 includes a recessed carrying handle which is fitted on the top of the robot. Whereas the 595 do not have this carrying handle.

Battery
The 655 comes with the XLife Extended Life battery while the 595 uses the yellow advanced power system battery.
So, what’s the major difference between the Xlife and APS battery?
Here’s info from iRobot
“iRobot XLife Extended Life Battery delivers twice as many cleaning cycles as previous Roomba batteries, doubling the time before you may need to replace your Roomba battery.
*Roomba runtime remains the same between recharges. Battery lifetime varies with home environment and usage.”

Accessories
The 595 is one of the iRobot Roomba models that come with the most accessories.
It includes 2 Virtual Walls with 4 Duracell C batteries, 4 AeroVac filters, 3 Side Brushes, 3 Rubber Brush, 3 Bristle Brush.
While the 655 has only 1 Virtual Wall with 2 Duracell C batteries, 2 AeroVac filters, 2 Side Brushes, 2 Rubber Brush, 2 Bristle Brush.

Color
The faceplate of the 655 is Gray while it’s Black on the 595.

If you know more difference between these 2 iRobot Roomba robotic vacuum cleaners, please share your review here.

The difference between iRobot Roomba 645 and 650 are as follows.

Roomba 650 vs 645
images from manufacturer

On-Board Scheduling
The iRobot Roomba 645 which is a Sam’s Club exclusive is a similar model to the 630. It has NO on-board scheduling whereas the 650 features the On-Board Scheduling that allows you to preset the cleaning time for Roomba to clean whenever you want.
You can see this difference from the faceplate of the two units.

Battery
The iRobot 645 uses the Xlife Extended Life Battery whereas the 650 comes with the Advanced Power System battery.
The running time of these batteries per charge are the same, the Xlife battery however, has a longer overall battery life.

Side Brush
The 645 uses a new easy to remove side brush that has a flat head screw while the Roomba 650 uses the brush with a crosshead screw.

Price
The 650 is more expensive.
The 645 is priced at $329.98 at samsclub.com whereas the 650 is priced at $399.99 at irobot.com

Brush Cleaning Tools
The 645 comes with 2 brush cleaning tools ( 1 round and 1 flat), while the 650 comes with only the flat brush cleaning tool.

Color
The 645 faceplate is in gray color whereas the 650 faceplate is in black color.

If you know other difference between the Roomba 650 and 645, please share below, thanks.

As far as I know, the key difference between iRobot Roomba 655 and 645 is that the 655 features the on-board scheduling whereas the 645 does NOT have the scheduling.

Extra Accessories
The iRobot 655 comes with 1 extra Side Brush, 1 extra Bristle Brush, and 1 extra Rubber Brush whereas the 645 does not include extra brushes.

Price
The 655 is $20 more expensive than the 645; the 645 is a Sam’s Club exclusive unit, while the 655 is sold at Costco.com.

If you know other difference between iRobot 645 and 655, please share below.