I have used lastminute for hotels and they are OK, althoguh on a couple of occassions the hotels have not been gracious about this method of booking!
As for flights, never ever again would I even consider it. A couple of very long stories which I won't bore you with, but simply put - if you want them to sell a flight to you, fine, they are great - but don't go looking on their site for something to suit your needs.
PS: Based on the few experiences I have of speaking to them on the phone, they are useless - I accept that this is a limited exposure, and am happy to be proved wrong by glowing testomonials (or not).
Nick