readme updated

README.md

@@ -19,7 +19,24 @@ to use, host and modify. Additionally, the following features were added/changed
 (13 word mnemonics generated by MyMonero work as usual though).
  - import wallet fee was reduced.
  - support of testnet network and wallets was added.
- - corrected handling of mempool, coinbase, locked and unlocked transactions.
+ - improved handling of mempool, coinbase, locked and unlocked transactions.
+ - added dynamic fees for testnet.
+   
+   
+## Limitations
+
+#### Performance
+
+Open Monero is not as fast as MyMonero. This is because it is basic, easy to understand
+ and straight forward implementation of the backend. Thus, it does not use any fancy catching
+ of txs, blocks, complex database structures and sql queries. But adding this in the future,
+ should not be a problem once all the basic operations work.
+   
+#### Coinbase tranasaction
+   
+Coinbase txs are not used for making transactions. Current don't know
+how to process them in the backend, so that frontend correctly uses them to construct txs.
+Maybe frontend handling of ringct coinbase txs is buggy?  
    
 ##  Status