Let me start with this note:
"Asking a Pharo Group what fits best for a good commercial solution is like asking an hungry person whether he would like to go for a feast.."
Most certainly the answer should be a resounding yes from this group. You should.
Now if you are asking if there are alternatives: They abound from all sorts of frameworks for websites, shopping carts, ecommerce stuff extending even to the Apache Ofbiz freeware to the paid, Oracle, MS wares.� What is a best fit entirely depends on your inclination and willingness to plumb the depths.� RubyOnRails, Grails .. umpteen others have frameworks, plugin modules galore to work with. Pharo - Seaside offers a very different proposition, ease of development, debugging and building incrementally.
If you use Oracle, MS , IBM or likes, blame them when things go wrong and carry on. With Pharo you will have to pull up the sleeves, ask for help in this forum that I am sure will be forthcoming to some extent free and� lots more if you can pay.
Having said this: When I had my say on this 4 years back in one of the major Conglomerate in India, I proposed Apache OfBiz, which after basic prototyping the whole project was shelved due to lack of understanding in the group, of directions to take, I believe there is nothing like having a plan of action that mixes n matches� Pharo with Apache Ofbiz that you can later throw away once you are fully built up in Pharo. For scalability and future Gemstone is a good fit, but that may take quite a while. Pharo will scale well if you can follow a clean architecture plan.
The added glory is you can be the author / owner of the Pharo - Ofbiz bridge too.. ! Bit of XML RPC tricks should help and take help of Groovy on the Ofbiz side, you will feel Java malleable enough like it ought to be.