Tibet was a series of surprises for me. It's just lack of education, but it was almost nothing like I had expected. The varied terrain is well beyond what I could have imagined. From snow capped Mt Everest to arid deserts and everything in between. I can't count the times in the car I said "I had no idea Tibet would look like this". The next surprise was that, make no mistake, Tibet is China. It is not "becoming China", it IS China. The emigration programs by the Chinese government have been successful. We saw far more evidence of Chinese culture than Tibetan. Stores, restaurants, road signs and entire suburbs of Lhasa are predominantly Chinese and catering to the masses of Chinese tourists that flock here on vacation. The monks are Chinese, not Tibetan. Most Tibetans we saw or met were small souvenir stand operators, pilgrims, beggars or farmers. I don't think we saw any Chinese farmers, though... On the one hand, this Chinafication was a bit disheartening, but the reality is just that it is just the evolution of a culture. Tibet must be considered as a Chinese territory to be partially understood.
Our route through Tibet followed a fairly standard itinerary. We first spent a few days in and around Lhasa on our own. We spent a few more days than planned because John refused to get out of bed until we threatened him with an IV at a Chinese hospital. Altitude sickness hit him pretty hard. Once everyone was healthy and happy, we hired a 4x4 with driver and government-mandated "guide" to take us for a 7 day drive to the big sights en route to dropping us off at the Nepal border. The "guide" is apparently a babysitter to make sure you don't unfurl a "Free Tibet" flag or cause any other unwanted publicity. After nearly getting us deported from Tibet at the Everest base camp ranger station, I can't so much vouch for her credentials as an actual guide.
In a nutshell, Tibet was much more than we expected, but arguably too much work. The geography and scenery are incredibly varied and truly amazing. The religious culture and monasteries (although they all look the same after the 2nd one!) are beautiful, interesting and very active. The Chinese government makes getting to and traveling through Tibet very difficult for foreigners. There's a system of permits and guide requirements that almost force the use of a travel agents and guides. The Chinafication detracts from the romantic visions most westerners have of Tibet, keep an open mind and it's an interesting place.
Should you go? Well, personally, I'd say skip unless there is something specific about Tibet you want, like being able to drive practically to the base of Everest. If it's just a taste of the culture and experience in the Himalayas, Nepal is much more accessible and less touristed. Although you can't drive to Everest in Nepal.