i've used the rotozip and actually liked it. I also have a set of those porsadrills which I put in my variable speed mains powered Bosch drill (it can go real slow) and like them too. Now the thing is this, the rotozip cost about a ton and the bits are quite expensive so for the same capability (for drilling holes) you can buy yourself a decent quality drill (which has loads of uses) and a set of porsadrills! Now the porsadrills probably wont last as long as the rotozip Bosch cores but the Porsadrill cores are cheap enough to amortise into a customers job and you can afford to have a set of common sizes! Now on the other side the Rotozip does have an excellent set of router type tools which used with the cheap looking handle attachment do a great job at routing things like board! ... so ... if your prime focus is drilling holes then Id go buy a nice drill (which has many more uses than the Rotozip) and bung some Porsadrill cores in it (especially if you can charge them every now and again to a job), but if you like the router capability then Id go for the Rotozip.
just my opinions.
p.s.
... and to throw you another curve ball - i got a tip-off that a well known orange and black shed sells their own make copy of a rotozip at half price, same size chuck etc (to take Bosch bits) which i have yet to check out.
p.p.s
... and the service from 365drills is excellent, i needed drills fast for a quick
bathroom job, got them pretty much overnight by paying more on the postage, got a quick private email from them letting me know they were being packed (cos I pinged them to ask) so didnt have the worry of chasing them! that means a lot to me. 365drills understand customer service.