Yes it does make a difference! Not huge for sure. But if you are stuck at certain levels than yes it helps. I swapped from a 50 to a 52 with lots of hesitation. First thing I noticed was that for sure it was harder! Now that I am used to it, I am recording better and stronger rides that previous. I have absolutely no regrets in doing so and wish that I could possibly go higher than my current bike restrictions allow.

Better and stronger rides? How did your change from 50t to 52t contribute?
What now restricts you going to a chainring larger than 52t?
Kudos for using the search facility, btw.
And for the OP, who 16 years posted the question and never came back (logged in) to see the advice:
If I changed my [ 50 tooth chainring for a 52 tooth one], would I need a slightly longer chain and would these 2 extra teeth make much difference?
Chain: no, provided when on large-large now the RD cage is not less (earlier) than 4:30 o'clock. If already at 4o'clock = chain one (inch) link longer required.
Top gear ratio: Will increase by 4% (@hgf tick), probably from 123" to 128". This will make no difference to your riding.
FD: The circumference of the chain ring will increase from 25" to 26", where the chain sits. The radius (centre to tooth tip) of the 50t ring is 104mm (apologies for flicking to metric) and as said the new ring's radius will ~4mm more and the FD
will need to be shifted the same amount higher.
Chainset: The 10sp chainset will be fine with a 9sp chain. The new Ultegra chainset, also square taper, may need a different BB spindle length.