I was really impressed with my Plus 2 although there could have been a little more filter media. They're easy to use and easy to maintain. Plenty of pet stores stock spare filter media and spares. I don't think I'd bother with any other internal filter given the choice.
You can read about a review that Practical Fish Keeping did on them along with all the other commerically availalbe filter systems here: PFK Review
In the subject you ask if the Plus 3 would be ok for a 10 - 15 gallon tank. A fluval plus 3 might be a bit too powerful as it is intented for use with tanks upto 28 gallons. A plus 2 would probably be better suited for this task (up to 20 gallons).
You can get the specs for these filters on here: Hagen
I have a 2+ on my 15g and it's ace. Cycles the tank water 8 times per hour, never had any problems with it. I wouldnt put a 3+ in because there is already a very strong current in mine jsut from the 2+ but i guesss it depends on the fish
Great thanks for your advice I'll see if I can get hold of a 2 plus for the same sort of price
Currently e-mailing someone about a 15g setup they're advertising for £15 so I hope I can get that and not have to worry about a new filter. But if the filter sucks then I'll get a 2 plus!