What do you mean by simple ecommerce? Do you want to sell a few products, a membership, consulting service, etc? I can make a more specific recommendation if I knew a bit more details.
I'll say that personally I have enjoyed using Wufoo for some simple ecommerce needs - just sync it into Paypal or Chargify and you can create a simple sales form. You may want to consider something like that. Gravity forms also has a paypal integration, but a bit simpler.
There are probably 40 products in total. No subscriptions, membership or anything like that.
I'd love to just use paypal as a payment solution but the client needs to use TransAccept the clydesdale bank system. They offer hosted payment pages, so if there is anything that would intergrate neatly with that it'd be a bonus.
I've looked at the payment gateways of all of WordPress shopping carts and I haven't seen one that supports TransAccept/Clydesdale. You'll most likely have to convince your client to use another payment processor or build the integration yourself.
Shopp plugin offers the most options when it comes to payment gateways. If you wanna build the integration yourself, I'd recommend you also look into MarketPress and Cart66. The code of these two is well documented and has good API, which makes them extensible.
Last edited by Mittineague; May 6, 2011 at 02:26.
Reason: removing unnecessary link