Advice on buying a new bike I am looking to buy a new brand new bike but I'm not experienced at all with bike specs and quality and things to look out for etc. I have previously only had second hand really basic bicycles in my life that have done the job but I've always gone from issue to issue with then and I decided to stop putting money into a bad bike and spend a little extra on a brand new bike. My needs are not that extensive. I need a bike to go about 15km a day, 6 days a week to and from college. I'll be travelling on road surface but I don't really want a racing bike per say. My budget is 300€ but I have no problem (and I kinda wanna) spend right up the budget to get a bike that I know will last. What I really don't want to is to have problems of any kind (with the exception of flat tyres obviously because this is not the manufacturers fault) really in the first year or 2 of buying the bike.

What I have been looking at so far: http://www.halfords.ie/cycling/bikes/mountain-bikes/carrera-vengeance-mountain-bike-2011-2012-large-20#tab4

This bike seems to fit my needs but is it good? the reviews would lead me to believe that its no professional show stopper but its not gonna break in the next 2 years or so. It is also being sold from a respectable company (Halfords, not Carrera).

Bottom line question: should I buy this? Is it good?
Mountain bikes are fine for road commuting too.  The advantages are fatter tires which make the bike more stable and the upright riding posture, which many find to be more comfortable compared to road bikes.  This disadvantage is mountain bikes aren't as efficient.  You'll need to expend more energy to get to the destination compared to a road bike, due to wind resistance (from the upright riding posture) and tire friction (from the wider tires).  You may get there on a slightly slower ride too, so it will take a tad longer.  Still, I think a mountain bike is a good choice based on what you say. 

What I'd look for is a good quality aluminum (or cro-moly steel if they still make them) fully rigid frame, and , most important, Shimano's economy components all around.  Skip everything that is unnecessary, like disc brakes, hydraulic brakes, 10 and 11 speed cassettes, etc.  Stay with traditional cantilever or V-brakes (really just another type of cantilever).  The more basic, the better.  You could easily get by with 10 total speeds, in a 2 x 5 configuration, though I doubt you'll find that available, but the few speeds, the more robust the drivetrain will be.  For the frame, the more standard, the better.  Avoid unusual drop out dimensions, etc.   And, most important of all,  the more the component set is one that sells in large volumes, the better.  It will be much easier to obtain parts in the future.

After that the most important thing to look for is fit.  Take a test ride on at least 3 or four bikes of various sizes before deciding.  If you think you might want to use the bike for actual mountain biking -- like riding on steep dirt trails -- error on the "too small" side rather than the "too big".  Otherwise, just choose the size that seems to fit best from the test rides.