The amazing part of the Roomba is how shockingly well iRobot supports them. You can get a ton of spare parts for them, and it is easy and inexpensive to repair or even upgrade a Roomba.
You read that right: Roombas are easy to work on AND the parts are inexpensive.
That's like buying a BMW, and learning that cylinder heads and alternators are $50 each and can be snapped in within 5 minutes.
I've had my Roomba 600 series for five years. Now five years is a lot of time for a computer technology product that deals with dust and dirt. Here are the things that I've done so far:
Replaced the battery
After about 3 years, my Roomba's original battery was getting pretty weak. I replaced it. Replacing it is a simple affair, taking about 5 minutes. New batteries are readily available at low cost.
Replaced (and upgraded) the brush head
Evidently I used my Roomba too much in my extremely dirty basement. My Roomba's original green-colored brush head stopped working well. I opened it up and it looked like the gears were getting chewed up with dust.
Therefore, I decided to buy a new brush head. The brush head is basically the entire cleaning system of the Roomba. It is possible to upgrade the classic brushhead to the Areovac version.
Sounds expensive and hard to deal with. But it's not! The new cleaning head was under $40, and it took about 5 minutes to install.
Even better, the new brush head was the modern Aerovac version. That's right - this repair upgraded my Roomba's cleaning technology.
Replaced the power jack
I'm not sure what happened here, but my Roomba's original rarely-used power jack failed. It was somehow sending a signal to my Roomba that he was still plugged in to the charger, when he wasn't. This led to docking issues.
This was easy to install, but it took a little more time - maybe 15 mintues. The replacement jack was about $5.
iRobot is the best. They stand behind their products, and their products are improvable after purchase. One thing I'd love is an upgrade to Roomba's brain, so that he could be controlled via bluetooth or wifi. That'd be real fun!