Here is a long list of all the changes, fixes, and updates the various patches will accomplish (including some gameplay tweaks). The short answer, IMHO, would be yes, it is definitely worthwhile to patch (and you won't 'lose' anything aside from exploits anyway AFAIK).
As to attack bonuses, you have to be a bit careful about that one. Try to note whether a unit says "+50%
attack against X" or just simply "+50% against X." For example, chariots get a bonus only when attacking axes, but not when defending against them (their tooltip info says "+50%
attack"). Most units will just generically say "+X% against X," in which case they do indeed get the bonus when attacking or defending (e.g. anti-mounted always get +100% against mounted units, regardless of whether attacking or defending, IIRC). [Also, note that these bonuses are applied against the opponent, as opposed to toward your unit, so actually a +100% conditional bonus (i.e. not a Combat-promotion permanent bonus) would actually be applied against your opponent's strength (and would halve it) as opposed to augmenting (doubling) your own unit's strength. Relatively minor, but good to be aware of IMHO.]
Argh; beaten by
one lousy minute!!

Nicely done,
cabert.