The only benefits that I'm aware of when consolidating federal loans with a federal consolidation loans are:
1) All your loans will now be with the same servicer, so you have only one monthly payment (all my loans were with the same servicer anyway, so I only had one payment...)
2) Simplicity--you just have one big loan now instead of lots of small ones. (Though a big loan is quite scary, and studies show people pay off their student debt quicker by paying off small loans first. The smarter thing to do is pay off higher-interest rate loans first, but most people aren't disciplined enough and in the end benefit from the "snowball effect" of paying of the smaller loans, feeling like they're making progress, etc.
3) You can bring non-direct loans into the direct loan program, so that they can be eligible for PSLF, PAYE (non-direct loans will already be eligible for IBR)
The drawbacks are:
1) Your interest rate actually goes up (gets rounded up as you mention). Unlike private consolidation loans, the federal consolidation loan doesn't let you consolidate at today's rates--it just takes a weighted average, rounded up
2) You have a new loan, so any prior payments towards PAYE/IBR/PSLF are not tossed away and you start over
3) Your interest will basically capitalize since all that accrued interest will now be part of the principle of the consolidation loan (note: your interest capitalizes at the end of your grace period anyway, so this is really a moot point if you're a recent grad, and could technically help you if you consolidate right when you graduate since it'll save you from those extra six month's worth of interest accrual before capitalization)
4) You lose the ability to selectively pay off higher interest rate loans first. Why pay off your 5.5% loan first when you could pay off that one near 8%?
I took out a consolidation loan, which unfortunately included consolidating a non-direct GradPlus loan (8.5%) with my stafford loans (sub/unsub). I did this because my MS1 loans were not direct loans, and I wanted to bring them into the direct loan program so they could be eligible for PSLF, if it sticks around. I figured it was worth it. I only consolidated those loans--my MS2-4 loans were all direct loans so I didn't include them.
I personally would not have consolidated my loans for any other reason. I have no idea why your financial aid office is telling you to consolidate--my financial aid director was very adamant about NOT consolidating with the exception of bringing your non-direct loans into the direct loan program, for the sole purposes of benefiting from PSLF or the revised IBR program (PAYE).
Now, if you're talking about private consolidation loans (DRB has a new program for residents), you could actually benefit from a much lower interest rate, but then you also lose all federal loan benefits (IBR, PSLF, etc.), so that isn't a program worth looking into until you know if you will be aiming for PSLF.