The standard LAMP components have barely changed the past few Ubuntu releases, pretty much every component has stayed on the same upstream feature-version and has had no major packaging changes either. However with an unstable kernel, stable components wont help. Ubuntu 12.04 did base theirs off one of the better upstream releases in a while though - 3.2. At work I've been running 12.04 on a dozen servers, vm's and containers since RC, and had no major issues crop up so far. Some of them running fairly busy data warehousing on Oracle 11g2*
I'd say for a LAMP type setup, the risk of stability issues is fairly low in 12.04.
* That however is quite risky, support wise. But it does work
