I have had three different pool cleaners:

Manual vacuum brush on the end of a long hose ---Pain in the back!!
Dolphin Diagnostic $700 ---- Got stuck on everything and damaged my liner
Aquabot T-4 $1500 ---- wish I had started out with this!!

The T-4 is by far the best cleaner IMHO --- with the remote and high speed plus add in the random turns and horizontal action even on the side walls, you can't beat it. So far service turnaround has been less than 2 weeks (I damaged the cord [They fixed it as warrantee] just had to pay shipping 1 way)