Talisman is weak without a strong setup, but it can give you some value gain/pile depletion that can be very helpful in select situations. For instance Forge/Talisman can be a cheap way to convert overdraw and light cash into province fodder (e.g. you have a Forge enabled engine with components at $4, spending a spare $4 on a Talisman can allow you to score provinces a turn delayed for $4; yes this comes a turn later and you could just forge Prov-> Prov instead ... but it is an option to try to eke some odds of a come from behind win). Likewise, it can play nicely with Procession where you can flood the deck with actions (e.g. more Prssn). When you care more about total value of the cards in the deck than total cash production (e.g. Forge, Salvager, Apprentice, Graverobber, etc.), the multiplicative effect of Talisman can lead to really quick ramp up.
Talisman is a beast at piling out on the sly. For the price of $4 (or so), Tr->Mine can triple the remainder of your buying power. If you have buys to spare (say I have a Margrave engine) this can lead to a lot of "safe" piles dying abruptly. For instance, if I have a $22 engine and I tank two silvers I go down to $20 (instead of up to $25 with a Plat) and spread over 5 buys, that let's me knock off $80 worth of cards - "two" entire untouched piles can go down without warning (in reality it is more likely something like gain 6 Tr and 8 Talisman or just gain 8 Talisman, buy a province). The non-linear scaling ramps up a lot faster than people tend to expect so you can very abruptly kill piles in 4-6 card range.
If the other guy is aware of this, then he isn't going to leave you a nice way to ramp up off a Mine, Iw, and pile before he has points. Thus I expect that for most folks getting burnt once or twice by an unexpected ramp up is enough to alter their play (say greening sooner or giving their deck more flexibility with gainers), but Talisman being there at all means you should be mindful of quick ramp ups.
The best generic support for Talisman I've found are Tr, Prssn, and Hwy. For fun, compare Talisman to the new card, Duplicate. Duplicate does its magic a turn later than Talisman, is worth $1 less for buying, requires an Action to play, and will miss more shuffles. That is a lot of penalty with only a couple of major benefits obvious - gaining up to $6, works on Green, works on any gain. Tr, Prssn, and Hwy can get rid (somewhat) of the penalty for gaining only $4 or less and make Talisman better. Gaining a Tr can be functionally close to gaining a second $5 - $8 action card, Prssn not only can play expensive cards when appropriate, but quickly turn mediocre $4s into power $5s. Hwy allows you to gain the big stuff (most notably more Hwy) and Talisman makes a very good buy on a busted hand where you miss $5 or to pick up when Hwy costs $3 and you have $5/2 buys. Rolling the dice to recover a whiffed Hwy buy is not at all bad, as a bonus the lack of +buy on Hwy means that Talisman may be able to function as a no-other-option +gain that can fuel megaturns (e.g. gain 2 Kc this turn, gain two Sab next turn).
