Vishera is a great drop-in upgrade but the situation changes if you need a new mobo - at that point you have to consider Intel. It offers next to zero incentive for anyone with a 2600k or better to consider switching platforms. The price is very attractive and cheaper than many comparable Intel parts, but then again that $50-100 savings doesn't mean much when many have been enjoying the same or better performance with SB for 12 or 18 months.
Trinity isn't socket compatible with Llano, and as a Llano owner you'd be much better off upgrading to a discrete than upgrading to Trinity. Llano's 4c/4t is generally better than Trinity's 2m/4t setup in MT situations. It only brings a 16% average IGP increase over Llano - and plenty of users fall into the situation where the Trinity IGP is either too much (web/office/media usage) or too little (not quite enough for 1080p/medium). And the value proposition for both Llano and Trinity drops once a discrete is added.