(http://wiki.dominionstrategy.com/images/thumb/1/11/Loan.jpg/374px-Loan.jpg)
Loan is much-maligned trasher. It is constantly criticized for what it can't do, but seldom praised for what it does well. It's a card that occasionally "feels bad" when you play it. Perception, however, does not always match up with performance. Let's look at the specific things this card can and cannot do.
Cannot:
- Loan cannot trash Estates
This is obviously a major thing not to have. Trashing Estates is excellent for your deck. However, there are plenty of respectable to great trashers that can only trash Copper (Moneylender, Spice Merchant, Counterfeit).
- Loan cannot avoid skipping your good cards
Skipping a valuable card hurts, especially on your first shuffle, where you do not yet have the ability to cycle your deck quickly. However, there is only a 5/48 (about 10.42%) chance of Loan skipping your $4 buy on the first shuffle. That chance goes up the more good cards you have, but the impact of skipping cards goes down.
- Loan cannot always trash Copper with Silver in your deck
This is actually not a big deal. First of all, when you're going for an engine (i.e. when you would buy Loan) you generally try to go as light on Silver as possible. Second, even if you buy a Silver, you only have a 1/8 (12.5%) chance of hitting it with Loan. Lastly, you may not even need Silver since Loan has pretty good economy for a trasher.
- Loan cannot trash Copper from your hand
This comes into play late in the game when you're drawing your whole deck. It's kind of unfortunate, but generally most of your coppers will be gone by this point.
Can
- Loan can trash a Copper from your deck
This is quite a bit better than trashing from your hand for two reasons. One is that you don't have to reduce your buy power for this turn, and the other is that you don't have to draw that Copper on this shuffle.
- Loan can give $4 hands often early
Since Loan does not trash from your hand and it gives $1 of its own, it is actually pretty solid at having valuable hands early. In a deck of only the ten starting cards and one Loan, Loan's average hand value is $3.8.
- Loan can be played with an action
Loan is a treasure, therefore it does not require an action to play. One does not have to worry about colliding Loan with your $4 buy on the first shuffle, nor does one have to buy villages to ensure repeated plays.
The "cannots" are generally overblown and the "cans" underrated. This has led to Loan being ranked 37th out of 49 $3 cards. Normally to argue against this one would compare Loan to another $3 cards that's above it, but it has a far more comparable analog:
Loan vs Spice Merchant
Early in the game, Loan actually has an edge on Spice Merchant. While Spice Merchant has to decide between drawing and non-terminality or a consistent $2, Loan gets non-terminality, $2, and cycling always. As the average value of the deck rises above Copper, +2 Cards becomes more valuable than $2. Once the whole deck is being drawn, Spice Merchant can give +Buy while Loan cannot hit the Coppers in hand. Even though Spice Merchant is clearly the better card overall, it's a testament to Loan's strength that it can compare to one of the stronger $4.
As for a comparable $3, the closest is probably Lookout, which is 17 ranks above Loan. Each has advantages over the other (Lookout can trash Estates but has trouble finding them, Loan can't trash Estates but can easily find Coppers), but overall they are about the same power level. Forager is another comparable card (rank 10) that can trash Estates, but provides no economy until someone trashes a treasure.
TL;DR: Loan could stand to move up 15 or more spots on the rankings.